In foil printing, a colored foil bonded to a backing, hereinafter referred to as a “foil backing” is transferred from the foil backing to a substrate to form an image or parts of an image on the substrate. Hereinafter, the colored foil and its foil backing are referred to as a “printing foil”. In foil printing on paper, generally, the paper is printed with a desired image using a conventional printing press and conventional printing inks. The image is then printed with an adhesive, hereinafter referred to as a “foiling adhesive”, in those areas of the image to which it is desired to transfer the foil. The foiling adhesive is usually a dry toner “printed” in a xerographic process, in which the toner is bonded to the paper by fusing. A printing foil having a desired color foil is then pressed to the paper and heated. The heating causes the printed toner to melt and become tacky. The printing inks on the other hand are substantially unaffected by the heat and pressure. The foil sticks to the tacky toner but not the printed inks. When the printing foil is removed, foil detaches from the foil backing and adheres to the foiling adhesive to cover the areas of the image that it is desired to foil print. Foils are generally metallic and are often used for special printing effects, such as for example, to print gold and purple metallic color details on feathers of an image of a peacock or to gild a name on a business card.
When foil printing an image, the transfer of a foil to only desired areas of the image requires that areas of the image that are not to be foil printed not stick to the foil when the printing foil bearing the foil is pressed to the image and heated. In many printing processes an image is printed on paper by depositing toners of appropriate colors on the paper and fusing the toners to the paper. Toners used to print an image are fused to paper similarly to the way that toner used as a foiling adhesive in a conventional foil printing process is bonded to a printed image. If a printing foil is pressed to an image printed with toners and heated, the toner melts and foil adheres to all printed areas of the image that contact the printing foil. When an image is printed with toners it is therefore not practical to foil print only parts of the image using conventional foil printing processes. It is certainly not practical to foil print only fine details of such an image, such as for example details of the feathers of the peacock image noted above.